Eukaryotic DNA is packaged into chromatin, and this chromatin has a well-defined organization. Chromatin is composed of nucleosome building blocks, whose positioning along the DNA dictates the accessibility of gene regulatory elements, and ultimately the expression levels of genes. Nucleosomes occur in regular repeating intervals on genes. These arrays are highly regulated through many mechanisms including: post- translational modifications, deposition and eviction that are facilitated by chaperones, and re-positioning facilitated by chromatin remodeling complexes. We propose to further our understanding of nucleosomal arrays on a genomic scale. In aim 1, we will use our newly developed ultra-high resolution ChIP-exo assay to determine the subnucleosomal organization of histone marks along nucleosomal arrays across a genome. In aim 2, we will map the nucleosomal and subnucleosomal organization of chromatin remodelers using ChIP-exo. Their placement at specific nucleosomes, and their orientation on the nucleosome surface should provide insight into how they function on a genomic scale. In aim 3, we will use our recently developed genome-wide reconstitution of properly positioned nucleosomal arrays to probe biochemical mechanisms of chromatin remodeler-directed array formation. Completion of these aims is expected to provide an understanding of fundamental principles of nucleosomal array and their role in regulating gene expression.